diff --git a/tildes/scss/_base.scss b/tildes/scss/_base.scss
index 6db3fdb..df622a2 100644
--- a/tildes/scss/_base.scss
+++ b/tildes/scss/_base.scss
@@ -103,7 +103,7 @@ fieldset {
   margin: 1rem;
   margin-right: 0;
   padding-left: 0.4rem;
-  border-left: 3px solid;
+  border-left: 3px solid var(--border-color);
 }
 
 figcaption {